Radar imaging of fracture geometry and aperture to characterize rock fall hazards in mining

Ground-penetrating radar is used in an underground salt mine to detect and characterize mining-induced fractures concealed in the mine roof. Radar images reflections from <1 to ∼50 m into the salt. Fracture locations and apertures identified by radar are validated with logged drillholes and exposed fractures. Open fractures with apertures <1 mm are imaged. Depth migration from topography accurately positions the fractures within the mine roof. Radar images all previously known fractures and added previously unknown information. Radar works between rock bolts. Radar attenuation is quantified using reflections at many logged fracture intersections in drillholes. This enables the prediction of fracture aperture. Strong variations in aperture are observed along fractures. The imaged roof fractures are interpreted to be caused by extensional stress induced by the mine cavity. The ability of ground-penetrating radar to image and quantify fractures in the mine roof can improve mine safety mitigation.